1. Field of the Invention
The present invention relates to an information processing apparatus, and system that includes a first and second information processing apparatuses at a minimum, and a data communication system pertaining to the information processing system.
2. Description of the Related Art
An extended control apparatus extends a function of an image processing apparatus, which possesses such functions as printing, image inputting, filing, transmitting, and receiving of documents, and image conversion. The extended control apparatus possesses a network function enhancement, which converts a data of a communications protocol of a network that is used in a user environment, that is, a LAN, to a data that is appropriate to an interface protocol that the image processing apparatus possesses. The extended control apparatus possesses such functions as a storage extension function, which spools a communications data, and a load distribution function, which performs such tasks as taking on a portion of the processing load that is performed by the image processing apparatus or a client device; refer to Japanese Patent Laid Open No. 2003-99230.
IP Security, or IPSec, is a technology specification that performs secure communication over the Internet. IPSec is set forth in a plurality of RFCS, the most important of these being RFC 2401, Security Architecture for the Internet Protocol.
In a case that the extended control apparatus employs the existing art to perform encryption and decryption processing in place of the image processing apparatus, however, the extended control apparatus encrypts a plaintext data that the image processing apparatus transmits to the extended control apparatus, and then appends a new header, called a trailer, to the encrypted data. Consequently, the size of the encrypted packet may exceed the Maximum Transfer Unit (MTU) of the receiving communications medium. In such instances, the extended control apparatus transmits the packet in question in segments, each of which is no larger than the MTU, an operation referred to as fragmentation. Performing the fragmentation, however, requires saving the packet in a buffer, extracting a portion of the packet from the buffer that is of a size that can be transmitted, and reconstructing the packet, resulting in increased overhead.